The invention relates to a pressure-operated hydraulic or pneumatic power wrench comprising a drive part and a functional part, said functional part having a shaft that is driven by a ratchet lever and includes a coupling device, and comprising a measuring section detecting the torsion element.
A hydraulic power wrench of this type is known from DE 296 07 207. In this power wrench, the shaft extends transversely through the housing of the functional part. Outside the housing, a measuring section adapted to be twisted is provided at the shaft. In this measuring section, a torsion sensor in the form of several extension measuring strips is mounted on the shaft. The torsion sensor forms an electric resistor arrangement the resistance of which depends on the torque. A coupling device adapted to be coupled with a tool or a screw head is located at the end of the shaft.
This power wrench with measuring cell permits to measure the torsional moment acting upon the screw whereby it is possible to detect the tightening torque directly at the screw connection.
It is the object of the invention to provide a pressure-operated power wrench with drive part, functional part and a measuring section, which has small dimensions in axial direction of the screw and thus can be used even if the headroom (above the screw) is small.